How to install a beam to replace a load-bearing wall
As you sit there sipping your morning coffee you decide it has got to go. That wall. That pesky divider between the kitchen and living room. You’ve been thinking about it for years, and now you’re finally going to tackle this project. It’s doable for a reasonably talented woodworker or DIY’er. There are however some important aspects to be aware of.
This article uses information from the 2018 BC Building Code, which is available online for free. It’s based on the 2015 National Building Code, which is widely adopted across Canada. Local conditions such as the snow load need to be considered. A building permit would generally be required for this renovation, so it would be wise to talk with your local building official when planning the project.
Think Thick Plywood
Laminated Veneer Lumber (LVL) is essentially very thick plywood manufactured in a variety of dimensions.
Add Two Temporary Walls
Temporary walls in place on either side of the existing load bearing wall supporting the ceiling joists and roof rafters.
Position the New Beam
The first ply of the LVL is in place above where the now removed bearing wall was located. Each ply is about 56 kgs (123 lbs) so it is manageable for two people.
Secure it in Place
The installed LVL beam. In this case each ply is nailed to the next. Some designs may require the pieces of the beam to be bolted together.
Firstly, is it a load bearing wall? If not, it could save a tremendous amount of work and cost. The age of the house should give some clues. Roughly speaking, if the home was constructed during the 1960s or before, it was likely “stick framed”. If so, it means many of the interior walls, parallel to the roof ridge carry some load. Possibly just ceiling joists but also an actual roof load may be supported by the wall(s) in question. A home built in the 70s and beyond often employs manufactured trusses that typically span from outside wall to outside wall, meaning there would be few if any interior load bearing walls. Note, that if the wall is supporting a floor, there would be the load from that floor but also any additional loads imposed by possible roof loads.
Now that you’ve determined the wall you want to remove is load bearing, for simplicity, let’s assume the wall is supporting a roof load only. You will need to decide on the type and size of beam to support the load. The span of the opening will have the greatest impact on beam selection.
In general, built up beams using lumber could work for spans up to about 4-5 meters (13′-16′). See building code span tables. Steel beams can span considerably farther. However, there is only one span table in the code and that is for the support of floors. If the specified snow load in your area is not greater than the floor load (1.9 kPa or 40 psf) then a beam could be selected from the span table. If the snow load is greater, then an engineer will be required to size the beam.
Another possibility is Laminated Veneer Lumber (LVL). There are no span tables in the building code for these so an engineer will be required. Typically, the manufacturer will provide the engineering for the beam. This would be for a simply supported beam with no point loads or other complicating factor. Otherwise an engineer would be required to size the beam, and possibly its support.
There are other beam types such as Glu-Lam, Parallam or a girder truss. I have not included these as they are not typically used in this type of alteration.
There are advantages and disadvantages to each type of beam;
Built up lumber beam
Laminated Veneer Lumber (LVL)
Time for an example
We will make some assumptions for our example project. The opening in the wall we want is to be 16′ (4.8 metres). The width of the building is 20′ (6 metres) and the specified roof load is 30 lbs/sq ft (1.5 kPa).
The Specified Snow Load (SSL) is calculated using the ground snow load and the rain load for the location of the building. E.g. the ground snow load is 2.1 kPa. The rain load is .3 kPa. The roof factor is .55. Therefore, the SSL is [2.1 X .55] +.3= 1.45kPa. (30.4 lbs/sq ft).
The span tables, no matter what type of beam you choose, are all similar. Just use the SSL, the type of beam (sawn lumber or steel) and check the maximum allowable span.
For our example, we’ll start with a built up wood beam to see if that works. It can be seen from the span table that the largest span possible under the 1.5 kPa specified snow load would be 4.18 metres (13.7 ft). Therefore, a built-up wood beam won’t work in this case.
Next check a steel beam. The table below, 22.214.171.124. is typically used for floor beams. However, since the assumed floor load of 40 lbs/sq ft (1.9kPa) is actually more than the specified roof load applicable to our project, the table can be used to select a beam. From the table we can see a W150 X 22 beam will span 5.2 meters (17.06 ft). Therefore, we could use a steel beam to span the 16′ opening.
We know an LVL beam will be able to span the 16′ opening because the manufacturers’ engineer will design a beam specifically for the project. It was decided to use the LVL because it will be easier to install. Two people can carry and lift each piece of the three-member beam into place. The steel beam, while cheaper, would be harder to handle, even with assistance. Typically, the beam will be manufactured 150mm (6″) longer than the span to allow for a minimum bearing surface of 75mm on each end. The beams are made (and priced) on 600mm (2′) increments, so the beam will be 5.5 metres (18′) long and cut on site.
Getting to work
Temporary walls are constructed on both sides of the existing wall that is to be removed. Build the walls using stud spacing the same as the spacing for the supported roof rafters and ceiling joists. A single top and bottom plate is sufficient.
Now the existing wall can be removed and the joist cut to accommodate the new beam. Cut the joists such that the beam will be centered on the ends of the existing wall. (Depending on the width of the new beam, the wall may need to be widened at the bearing points by adding studs to the side of the existing wall.) The individual pieces of the LVL can now be installed.
The remaining two plys of the LVL are installed (nailed or bolted, as required by the engineered detail) and hangers nailed in place. The temporary walls can then be removed.
Points to remember
With a little planning and research a person with reasonable carpentry skills should be able to accomplish this alteration. Regardless of the size of opening you want, the process is virtually the same. Support the floor or roof, install the appropriate beam with adequate bearing and then remove the temporary walls. If you want to tackle the install, most building inspectors will be happy to help with advice.